In Reply to: Re: Hydraulic Fluid Sources and Type posted by Larry Holbrook on March 12, 2019 at 15:35:24:
I am no oil expert - just like to understand how things work. And having spent 30 odd years in the technical specifications world I naturally gravitate to technical documentation when I go searching for information.
One other tidbit I noticed is the PDS for the Xtreme Heavy Duty UTTO states a sulfur content of .37% and ASTM D100 copper corrosion test result of 1B. The PDS for the economy fluid claims a D100 test result of 1A and does not list a sulfur content. While not conclusive that strongly suggests the heavy duty UTTO has a higher EP treat rate and one could expect a corresponding improvement in final drive gear wear protection. It also suggests they are using cheaper un-buffered (reactive) sulfur as the EP additive in order to get that performance. That would help to keep product costs down compared to mpre expensive formulations using buffered sulfur or sulfur alternative.
It's also interesting that none of the generic UTTO's claim an API GL performance level while the big boys all claim GL-4. The GL-4 service category is obsolete and the test rigs used to test for GL-4 conformance (old DANA axles) are no longer available. My understanding is the current industry "rule of thumb" is that you can claim GL-4 performance if your EP treat rate is some magical percentage of the treat rate used to obtain GL-5 performance. Perhaps the generic guys can't afford the API GL-5 testing needed to establish that baseline.